This invention relates to flexible couplings and more particularly to a disc-type flexible torque transmission coupling.
There are several different flexible couplings that have been used in the past to connect two shafts so that torque is transmitted between the shafts. The couplings can be divided into two general types: dfirst, the mechanical flexing couplings and, second, the material flexing couplings. Mechanical flexing couplings provide flexibility by allowing the components to slide or move relative to each other. An advantage of mechanical flexing couplings is that they generally permit greater axial misalignment between shafts than do material flexing couplings; however, the material flexing couplings have several features which have them preferable to mechanical flexing couplings. For example, material flexing couplings do not require lubrication, whereas mechanical flexing couplings usually require lubrication due to the frictional sliding motion involved. Some amount of clearance between mating gear teeth is always required in the mechanical flexing couplings, both in the interest of manufacturing tolerances and to allow for lubrication. This means that there may be torsional backlash in the mechanical flexing couplings, whereas there is no backlash with material flexing couplings.
The material flexing couplings provide flexibility by having certain parts designed to flex. These flexing elements can be of various materials, such as metal, rubber, or plastic. Couplings of this type generally must be operated within the fatigue limits of the material of the flexing element. Most metals have a predictable fatigue limit and permit the establishment of definite boundaries of operation. Elastomers (rubber, plastic, etc.) usually do not have a well-defined fatigue limit, and service life is determined primarily by the operational conditions. The material flexing group includes laminated-disc, diaphragm, spring, and elastomer couplings.
When a flexible disc is alternately bolted to two rigid members to form a flexible joint as in the typical flexible disc couplings, that flexible joint permits two types of misalignment between the two rigid members--axial misalignment and angular misalignment. In axial misalignment, the rigid members are separated an axial distance which is different from the design distance. In angular misalignment, the central longitudinal axes of the two rigid members do not perfectly coincide as they should but instead intersect at a point.
Examples of material flexing couplings are the flexible disc coupling disclosed in U.S. Pat. No. 4,055,966 "Fredericks", hereby incorporated by reference, and the diaphragm coupling disclosed in U.S. Pat. No. 4,196,597 "Robinson", hereby incorporated by reference. Flexible disc couplings are superior to diaphragm couplings in several respects. For example, flexible disc couplings are much simpler than diaphragm couplings. Also, the flexible discs are not hidden, thereby making it easy to visually detect failure in the flexible elements. Flexible disc couplings also usually occupy less space than diaphragm couplings, which is often an important consideration due to space limitations. However, the diaphragm couplings generally have the advantage of allowing greater axial misalignment between the hubs than the disc couplings.
The art has long sought, without avail, a flexible disc coupling having the ability to permit greater axial misalignment between the hubs. One approach to such a coupling would be to add an additional flexible disc and center member in series with the double-flexible coupling shown in Fredericks, thereby creating a triple-flexing coupling. This triple-flexing coupling should permit greater angular and axial misalignment than the double-flexing coupling, but I believe it would be radially unstable. Since there are three flexible joints in this coupling instead of two, the center portion would not remain in position on the central axis; instead, it might tend to be thrown outward due to centrifugal force.